1. Field of the Invention
The present invention relates to a magnetic recording element. In more detail, the present invention relates to an antistatic layer on a magnetic recording element using a synthetic resin support.
2. Description of the Prior Art
As magnetic recording elements, there are many kinds of magnetic tapes such as a recording tape, a memory tape, a video tape and a tape for a tape recorder, etc., a cassette tape loaded in a cassette, a cartridge tape loaded in a cartridge, a magnetic card or magnetic sheet in which a sheet support is used, and a magnetic disk in which a plate support is used. The kinds of magnetic recording elements are too numerous to describe in detail. However, all of these have essentially a constitution comprising a magnetic layer of a ferromagnetic substance as the main component on a support.
Hitherto, may suggestions on inventions for improving the properties of the magnetic recording elements when they are in use have been made. One of these suggestions is to apply an antistatic layer to a magnetic recording element when the support is composed of synthetic resins, by which the adherence of dust electrostatically to the recording element is prevented. Another of these suggestions is to provide a magnetic recording element which has a surface which can be written with pencils or with pens using water-soluble or oil-soluble inks.
Based on the above, a magnetic recording element has been suggested which comprises a layer containing an electrically conductive substance on a subbing layer on the back of a support having thereon a magnetic layer, and a layer containing a white pigment on the layer containing the electrically conductive substance.
However, it is very difficult to apply such coating layers to the support so that the thickness of the layers is thin. Consequently, the production yield of the elements is lowered and the thickness of the magnetic recording element becomes remarkably large. For example, in the case of a tape, it is sometimes difficult to accommodate a tape having a desired length in a tape loading reel having a desired size. Accordingly, it is desirable to decrease the thickness.
On the other hand, provision of an ideal magnetic recording element in which the support itself is white or light-colored and electrically conductive has been considered. In this case, a powder of a white or light-colored pigment and a powder of an electrically conductive substance are added to the support. However, if the pigment is added in a large amount in order to improve the whiteness, the support tends to have insufficient electric conductivity, while if a powder of carbon black or graphite is added in a large amount in order to improve the electic conductivity, a dark color tends to result. Further, there is a restriction that the white pigment and the electrically conductive substance should be used in the amount within a range such that the strength (tensile strength) of the support is not below a desired value. Accordingly, it is impossible to produce such an ideal magnetic recording element at the present time. This is because a low-priced electrically conductive white pigment having a stable property has not been found yet.